This invention relates to novel copolymers of maleic anhydride and the cyclic adducts of maleic anhydride and certain conjugated dienes, and more particularly to novel copolymers of maleic anhydride and the cyclic adducts of maleic anhydride and cyclic conjugated dienes. This invention also pertains to a process for preparing such copolymers.
The reaction of maleic anhydride with cyclic conjugated dienes such as cyclopentadiene and the isomeric methylcyclopentadienes yields the equimolar cyclic Diels-Alder adducts, endo-cis-5-norbornene-2, 3-dicarboxylic anhydride and the 1-, 5- and 7-methyl substituted homologues, respectively. The endo maleic anhydride-cyclopentadiene adduct, m.p. 165.degree. C., undergoes isomerization at elevated temperatures to the exo adduct, m.p. 143.degree. C. the isomerization takes place in the melt (D. Craig, J. Amer. Chem. Soc., 73, 4889 (1951)) or in solution (C. Ganter, U. Scheidegger, and J. D. Roberts, J. Amer. Chem. Soc., 87, 2771 (1965)). When either isomer is heated at a sufficiently elevated temperature, isomerization occurs and a mixture of both isomers is obtained. When the heating period is extended the equilibrium composition for that temperature is established. The various endo maleic anhydride-methylcyclopentadiene adducts, prepared from the 1-, 2- and 5-methylcyclopentadienes, similarly undergo isomerization to a mixture of the exo and endo adducts at elevated temperatures (V. A. Mironov, T. M. Fadeeva, U. A. Stepaniatz, and A. A. Akhrem, Tetrahedron Letters, 5823 (1966).
One object of the present invention is to provide novel copolymers of maleic anhydride and the maleic anhydride-conjugated diene cyclic adducts.
Another object of the present invention is to provide novel copolymers of maleic anhydride and the cyclic adducts of maleic anhydride and cyclic conjugated dienes.
A further object of the present invention is to provide a process for preparing such novel copolymers.
These and other objects of the present invention will become apparent from the ensuing description and illustrative embodiments.